The present invention relates to an infusion pump and method for continuously infusing a patient with a drug over a relatively long period of time, and more particularly to an infusion pump and method in which drug dose and rate calculations are performed based on infusion parameters input to the infusion pump by the user.
An infusion pump is used to continuously infuse a patient with a particular drug over a relatively long period of time, such as several hours or days. The drug is infused by the pump from a drug supply, such as a disposable plastic bag containing a predetermined volume and concentration of the drug. The duration of the infusion may necessitate periodic replacement of the drug bag.
An infusion pump may have a number of modes of operation, including a manual mode in which the user of the pump specifies the drug flow rate at which the pump is to infuse the patient and an automatic mode in which the pump may be programmed by the user to calculate the drug flow rate from a plurality of infusion parameters input by the user. The infusion parameters may be the drug dose and dose mode recommended or prescribed by a doctor, such as milligrams per minute, the concentration of the drug contained in the drug bag, and sometimes the weight of the patient. The manner in which some infusion pumps must be programmed in the automatic mode is relatively complicated and time consuming, which can be especially disadvantageous in emergency situations when fast action is required.
Some types of infusion pumps may incorporate a pumping mechanism which may not be able to pump fluids in continuously varying amounts. For example, the pumping mechanism may be able to pump fluid at a plurality of discrete flow rates, the smallest increment of which may be 0.1 milliliters per hour. Thus, in such a conventional pump where the infusion rate is automatically determined from a plurality of infusion parameters input by the user, the calculated infusion rate is typically rounded, for example, to the nearest 0.1 milliliters per hour. As a result of such rounding, the actual drug dose infused to the patient is not exactly equal to the intended drug dose input by the user of the pump, which can be misleading to the user if the actual drug dose is not displayed on the pump. In some cases where the intended dose is relatively small, the discrepancy between the intended dose and the dose actually administered to the patient can be substantial.